Imported Stp>expolde>Join>all one polysurf except one surface

hello all,

Im new to Rhino, but ive been recently using it to help smooth out surfaces I created in Solidworks.
Once i create the model (Solid) in SW I save as an STP and bring that into rhino. I need to explode the surfaces to delete the base surface of the model then rejoin them. But when i rejoin them, there is one surface which will not join back. It is shown as a surface where the others are shown as a polysurface’s. I have no clue why this is and its quite annoying.
If anyone has any ideas as to why this is happening, it would be much appricated.

FYI I tried saving the SW file as a surface by deleting the face i dont want and then importing this to rhino, but i still get the same issue. :frowning:

Hi Henry - please post an example here (public) or send to, with a link back here in your comments.


Hi Pascal,

Thanks for getting back to me. here is a screen shot of the situation. and the file in questions attached.
Surface Issue 1.3dm (1.8 MB)

Hi Henry - the surfaces are definitely well out of tolerance (0.00001, pretty tight) Is the new surface the strip in the middle? Can you send me, via, the original you are working with in Rhino, the step file, maybe there is something I can figure out that will help, workflow wise.